A meta-analysis of potential biomarkers associated with microplastic ingestion in marine fish.

Over the past decade, global reports have shown a rise in the harmful effects of microplastics (MPs) on marine fish. This study analysed marine species' biochemical biomarker responses to microplastic exposure, finding that MPs can induce oxidative stress in marine fish through meta-regression results. Overall, exposure to MPs resulted in the activation of antioxidant defence mechanisms, such as superoxide dismutase, catalase and glutathione reductase, detoxification enzymes such as glutathione-S-transferase, the detection of malondialdehyde, and inhibition of acetylcholinesterase. Moreover, results highlight oxidative stress biomarkers were activated in wild species that had ingested MPs, indicating potential harm to marine fish, as confirmed in experimental studies. Furthermore, even though MPs' exposure is better regulated in an experimental setting, it is challenging to replicate actual exposure and environmental factors. The study's findings show the need for more investigation into the hazardous consequences of exposure to environmental MPs on species surveyed in the maritime environment.

Plastic webs, the new food: Dynamics of microplastics in a Mediterranean food web, key species as pollution sources and receptors.

In the context of global environmental change, this study presents a novel approach to evaluating microplastic (MP) fluxes and probabilities of pollution within marine food webs. A topological model was built to understand the dynamics of MP pollution in the Mediterranean food webs. The analysis involves two approaches: the first approach includes centrality measures to understand the key role of species in the transmission of trophic effects regarding MPs, and the second approach incorporates MP data by developing the Interaction Pollution Indices (IPIs) at multiple levels to identify species being sources and receptors of MP pollution in the new concept of a plastic-food web. The trophic network consisted of 356 nodes representing not only species, but also aggregations in higher taxa, for a total of 3517 interactions, with 108 species having information on MP frequency of occurrence (FO). The mean probability of dietary MP transference was 0.087 %, and the maximum was 18 %. Species such as the rose shrimp A. antennatus, the catshark S. canicula, the sole S. solea, the sardine S. pilchardus, the Norway lobster N. norvegicus, and the forkbeard P. phycis were found to be significant sources of pollution and played crucial roles in the transmission of effects within the network. By incorporating the IPIs, a deeper understanding of the pollution dynamics at multiple levels was gained, highlighting the value of combining feeding and MP pollution data to develop effective management and conservation strategies. The application of the IPIs holds immense potential for studying bioaccumulation and biomagnification through MP pollutant transferences in marine ecosystems. Its flexibility in incorporating different types of information and units enables its transversal application throughout the field of ecology. This research provides a crucial step towards developing effective tools for MP pollution mitigation strategies and the preservation of marine ecosystems integrity.

Ingestion of microplastics and microfibers by the invasive blue crab Callinectes sapidus (Rathbun 1896) in the Balearic Islands, Spain.

The blue crab Callinectes sapidus Rathbun, 1896 is native to the western coasts of the Atlantic Ocean and is currently considered an invasive species in the Mediterranean Sea. In this study, we examined the stomach contents of C. sapidus to determine the frequency of occurrence of microplastics (MPs) and microfibers (MFs) in the Balearic Islands archipelago in the western Mediterranean Sea. A total of 120 individuals were collected from six locations between 2017 and 2020. Overall, 65.8% of the individuals had MPs and/or MFs particles with an average of 1.4 ± 1.6 particles ind.-1 of which an average of 1.0 ± 1.3 items ind.-1 were MFs and an average of 0.4 ± 0.8 items ind.-1 were MPs. In terms of type, fragments were the dominant type of MPs and the most common size of items ranged from between 0.5 and 1 mm (40%) followed by 1-5 mm (31%). The most prevalent polymers were low-density polyethylene (39%) and high-density polyethylene (26%). In terms of links to human activities, MP ingestion was positively correlated with an increase in drain pipes, whereas MF ingestion was positively correlated with an increase in sewage pipelines, providing evidence of potential sources and the bioavailability of these particles in various environments. This study confirms the widespread presence of MP and MF particles, even in areas that are currently managed under different protection statuses, in the stomach contents of invasive blue crab species throughout coastal communities.

Plastitar in the Mediterranean Sea: New records and the first geochemical characterization of these novel formations.

A new geological formation consisting of plastic debris admixed to petroleum oil residue, termed "plastitar", has been recently described in the Canary Islands. Here, we report its widespread occurrence across the Mediterranean coast and new insights into its biogeochemical composition. Specifically, we found marked differences in the diagenetic stable indicator profiles, suggesting a heterogeneous seeps provenance. Moreover, the 801 plastic particles found in the 1372 g of tar surveyed, with a maximum concentration of 2.0 items/g, showed interesting patterns in the tar mat, with nurdles predominantly layered in the external of the tar mat and lines in the inner core. Overall, the collected observation suggests that tar entraps plastics through a stepwise process and is a sink for them.

Stranded and floating marine debris detected along the coastline of Cabrera National Park (Balearic Islands).

Marine Protected Areas (MPAs) are managed to conserve ecosystems however increased reporting highlights the observations of marine debris within these areas. The coastline of Cabrera Natural Park (Cabrera MPA) was surveyed in February, March, May, and July of 2021 to evaluate the seasonal trend of marine debris between winter and summer months. A general value of 6.94 items/km, ranging from 4.38 ± 4.55 items/km in July to 12.57 ± 17.56 items/km in March, was detected with no statistical differences between areas or surveyed months. Abundance of stranded debris (77 %) was statistically higher than floating debris (23 %). Prevailed floating plastic pieces 2.5 >< 50 cm and stranded nets and pieces of nets >50 cm. Artificial polymer materials, non-sourced debris, and non-Single Use Plastics were the most common items identified. This study highlights the importance of applying mitigation measures to avoid the presence of marine debris in areas of ecological interest.

Mapping microplastic overlap between marine compartments and biodiversity in a Mediterranean marine protected area.

The Mediterranean Sea is adversely affected by human activities, of which the release of mismanaged waste into the marine environment, primarily plastic pollution, is one of the most omnipresent. The primary goal of this study is to link microplastic ingestion in several bioindicator species and creating hazard maps from microplastics sampled along the seafloor, in the hyperbenthos and along the sea surface layer in a Marine Protected Area (MPA). Considering the connectivity between these layers, the findings of this study identify areas of concern, especially within bay areas, where marine diversity is exposed to microplastic debris ingestion. In terms of exposure to plastic debris, our findings indicate that areas with high species diversity are particularly vulnerable to plastic exposure. The best model integrated the mean exposure of each species to plastic debris across each layer and the nektobenthic species inhabiting the hyperbenthos layer were found to be the most at risk. Furthermore, the cumulative model's scenario indicated a higher risk to plastic ingestion when all habitats were considered jointly. Overall, the findings of this research highlight marine diversity in a Mediterranean MPA are vulnerable to microplastic pollution, and this study's proposed exposure methodology is applicable to other MPAs.

Sea surface surveys for microplastic and floating marine macro litter items in coastal waters of Cabrera Archipelago Maritime Terrestrial National Park.

This study is aimed at identifying and comparing microplastics and floating marine litter along the sea surface in the marine protected area of Cabrera Archipelago Maritime Terrestrial National Park (Cabrera MPA) in the Balearic Islands. A total of 52 net surveys and 22 visual surveys were carried out between July and August in 2019 and 2020. The abundance of microplastic (MP) items was highest in the southern and eastern regions, with an average of 381,244.4 ± 1,031,082.8 items/km2 weighing an average of 927.1 ± 2731.4 g/km2. Most of these items were < 5 mm (81%) in size and were mainly composed of polyethylene and polypropylene (98%). In terms of floating marine macro litter (ML) from visual surveys, an average of 2028 ± 2084 items/km2 were observed. In this case, the majority of the ML items were plastic pieces (69%) measuring 2.5 to 50 cm. Furthermore, ML quantified by visual surveys was an order of magnitude higher than in similar studies carried out on large vessels, highlighting the importance of vessel height and speed for identifying the smallest size fractions (81%). The results of this study document the intensity of MPs and ML, primarily plastic, in coastal waters, and provide a baseline for management efforts to mitigate floating litter, in addition to raising awareness of the transferability of marine litter from other regions.

Are seafloor habitats influencing the distribution of microplastics in coastal sediments of a Marine Protected Area?

The marine environment is affected by the increasing presence of microplastics (MPs; < 5 mm), and the seafloor acts as a sink for these particles. Locations with different predominant seafloor habitat and protection level applied were selected from Cabrera Marine-Terrestrial National Park (henceforth, Cabrera MPA) (western Mediterranean Sea) with the aim to assess the distribution of MPs along the sediments of this Mediterranean MPA. A total of 37 samples were collected. A high diversity of sediment between locations was detected according to the Udden-Wentworth classification and locations were clustered into two main groups according to the predominance of different particle size fractions. The identification of MPs was carried out according to the sediment particle size classification. A total of 1431 MPs and a mean value (± SD) of 314.53 ± 409.94 items kg-1 D.W. were identified, and 70% of the particles were fibers. Statistically higher abundances of MPs were found in sediments collected from sandy habitats, with a mean value of 630.80 ± 636.87 items kg-1 D.W., compared to the abundances of MPs found in locations with different predominant seafloor habitats, that ranged from 136.79 ± 156.33 items kg-1 D.W. in habitats with similar predominance of seagrass and sand to 223.02 ± 113.35 items kg-1 D.W. in habitats with similar predominance of rocks and sand. The abundance of MPs regarding each sediment particle size fraction differed between years and locations, and the abundance of MPs according to each identified shape differed between sampling years, particle size fraction, and predominant seafloor habitat. The present study highlights the ubiquitous presence of MPs in seafloor sediments from a MPA. Furthermore, the results suggest that the predominant seafloor habitat can modulate the presence of MPs in marine environments in both general abundances and shape of items.

A Biomarker Approach as Responses of Bioindicator Commercial Fish Species to Microplastic Ingestion: Assessing Tissue and Biochemical Relationships.

Plastic debris is a growing environmental problem on a global scale, as plastics and microplastics (MPs) can be ingested by marine organisms, inducing toxic effects. The aim of this study was to assess MP intake and antioxidant responses in three bioindicator species: red mullet, bogue, and anchovy (Mullus surmuletus, Boops boops, and Engraulis encrasicolus, respectively) for plastic contamination in the Mediterranean Sea. MP intake was assessed in the gastrointestinal tract of the fish. Further, several enzymes from both the liver and brain were analysed. The antioxidant defences, catalase (CAT) and superoxide dismutase (SOD), as well as the detoxifying enzyme glutathione-S-transferase (GST), were measured in both tissues. The acetylcholine esterase (AchE), as an indicator of neuronal damage, was measured in the brain. Malondialdehyde (MDA) was analysed as a marker of oxidative damage in the brain and liver samples. Total MP intake and MP typology differed between the three species, with M. surmuletus showing the lowest intake of MPs, while B. boops showed the highest intake of MPs. An increase in both antioxidant enzymes was evidenced in E. encrasicolus liver activity with respect to MP intake. In brain samples, an increase in CAT activity was found in M. surmuletus and B. boops as a consequence of MP ingestion. SOD activity in the brain increased in B. boops and E. encrasicolus that had ingested MPs. GST activity increased in the liver of M. surmuletus' and in brains of B. boops that had ingested MPs. The intake of MPs is species related, as well as being inherently linked to the habitat they live in and being able to induce a light activation of species-specific detoxifying and antioxidant mechanisms.

Multispecies Assessment of Anthropogenic Particle Ingestion in a Marine Protected Area.

We have applied a multispecies ecosystem approach to analyse the ingestion of anthropogenic particles (AP) in the gastrointestinal tract of 313 individuals (17 fish species and 8 invertebrate species) from pelagic, demersal and benthic habitats in a marine protected area off the Western Mediterranean (Cabrera National Park). We have quantified and characterized the ingestion at several taxonomic levels of fish, sea urchins, sea cucumbers, bivalves, and jellyfish in relation to biotic/abiotic factors based on taxonomic groups, trophic guilds (functional groups) and habitats. AP ingestion occurrence ranged from 26 to 100% with no significant differences among taxonomic groups. The fish within the MPA showed an overall ingestion occurrence ranging from 0 to 100%, the echinoderms from 29 to 100%, the bivalves from 72 to 96% and the jellyfish 36% ingestion. The ecosystem approach applied to evaluate overall AP ingestion within the species reported that for trophic guilds, the omnivorous species ingested the highest amounts of anthropogenic items, while herbivores ingested significantly fewer items than all other trophic guilds. Moreover, no significant differences were found amongst habitats, indicating a homogeneous spatial distribution of APs at all studied habitats. The multispecies approach provided insight into the high APs exposure to species within Cabrera MPA, highlighting the potential harm linked with marine litter that threatens marine biodiversity.

Quantifying the risk of plastic ingestion by ichthyofauna in the Balearic Islands (western Mediterranean Sea).

This study investigates the risk plastic debris ingestion poses to coastal marine taxa in the Balearic Islands in the western Mediterranean Sea. Here, we use species observations and environmental data to model habitat maps for 42 species of fish. For each species, we then match estimates of habitat suitability against the spatial distribution of plastic debris to quantify plastic exposure, which we further combine with species-wise ingestion rates to map the risk of plastic ingestion. The results indicate that the risk of plastic ingestion is particularly high in the north-west and south-east regions and the risks varied strongly between species, with those at higher trophic levels being the most vulnerable overall. Extending this work to other coastal regions within the Mediterranean Sea and beyond will allow managers and policymakers to target the most appropriate areas and types of interventions for mitigating plastic pollution on coastal diversity in the marine environment.

Spatial distribution of macro- and micro-litter items along rocky and sandy beaches of a Marine Protected Area in the western Mediterranean Sea.

In this study, the spatial distribution and physical characteristics of beach macro- and micro-litter within the Cabrera Archipelago Maritime-Terrestrial National Park (Cabrera MPA), in the Balearic Islands have been analysed. For macro-litter items, a mean concentration of 1.9 ± 2.4 items/m2 weighing a total of 13 kg was quantified. In terms of beach composition, cobble beaches with deposited seagrass had almost twice as much marine litter as other beaches. For beach micro-litter items, white and transparent microplastics within the size class of 1-2 mm were the most abundant on all the beaches, and the most common polymer types were polyethylene (64%) and polypropylene (17.2%). Overall, for both macro- and micro-litter items, plastic was the most dominant material (90%) identified on all beaches surveyed within Cabrera MPA, indicating areas of low anthropogenic pressures are increasingly becoming sinks for marine litter.

Are the seafloors of marine protected areas sinks for marine litter? Composition and spatial distribution in Cabrera National Park.

The seafloors of oceans and seas are becoming major sinks for marine litter (ML) at a global scale and especially within the Mediterranean Sea. Within global oceans and seas, Marine Protected Areas (MPAs) have been established to protect and conserve marine habitats and increase marine biodiversity. In this study, extensive coastal shallow scuba diving surveys were conducted in 2019 and 2020 to identify the distribution of ML in the MPA of Cabrera Marine-Terrestrial National Park (Cabrera MPA) in the Balearic Islands. Approximately 900 items weighing 70.1 kg were collected throughout the MPA during the underwater surveys. Glass bottles, including pieces (25-30%) and glass or ceramic fragments >2.5 cm (8-19%) were the most common identified items followed by plastic food containers and plastic bags (~8%). Overall, 75% of the abundance of collected ML was observed during the first year. In terms of the protection status of the different locations, similar abundances of ML were found in public access areas and no-take areas. Additionally, no significant differences were identified according to location indicating that ML on the seafloor was homogeneous within the studied shallow coastal areas. Overall, the results indicate that Cabrera MPA is a hotspot for ML and mitigation actions and measures, such as annual cleaning efforts, can help to prevent and minimize ML accumulation on the seafloor.

Organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) occurrence in Sparus aurata exposed to microplastic enriched diets in aquaculture facilities.

Organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) are highly stable and bioaccumulative, and microplastics (MPs; plastics <5 mm) are ubiquitous in the marine environment. In this study we report the levels of a selection of pollutants in liver and muscle of juvenile gilthead seabream (Sparus aurata) exposed to virgin and weathered MP enriched diets during three months and followed by one month of MP depuration. In general, a major concentration of pollutants in liver was observed. According to OCPs, total DDTs was two or three times higher in liver. Levels in muscle suffer higher variability between treatments and sampling periods. The MP index was negatively correlated to HCB and positively to p,p'DDT in liver. Levels of pollutants are correlated to biological parameters such as total size and total weight. Our results suggest that the bioaccumulation is subjected to the molecular structure of the pollutants and that MPs are correlated with the detoxification system.

Assessment of the effect of long-term exposure to microplastics and depuration period in Sparus aurata Linnaeus, 1758: Liver and blood biomarkers.

The constant increase in plastic pollution has attracted great attention in recent years due to its potential detrimental effects on organisms and ecosystems. While the consequences of ingestion of large plastic litter are mostly understood, the impacts resulting from a long-term exposure and a recovery period of microplastics (MPs) are still limited. The aims were to monitor oxidative stress, detoxification and inflammatory biomarkers in liver, plasma and erythrocytes of Sparus aurata exposed during 90 days to low-density polyethylene (LDPE)-MPs enriched diet (10% by weight) followed by 30 days of depuration. Exposure to LDPE-MPs progressively activates the antioxidant and detoxification system and induces an inflammatory response in liver and plasma, whereas no significant changes were observed in erythrocytes. The plasma activities of catalase, myeloperoxidase (MPO), lysozyme and the levels of malondialdehyde (MDA) as maker of lipid peroxidation significantly increased after exposure to LDPE-MPs for 90 days compared to the control group. The activities of all antioxidant enzymes - catalase, superoxide dismutase, glutathione peroxidase and glutathione reductase-, the detoxification enzyme glutathione s-transferase, MPO, the production of reactive oxygen species and the levels of MDA were also significantly increased in liver after MPs exposure. Additionally, all these biomarkers tended to recover during the depuration period, most of them reaching similar levels to those of the control group. In conclusion, the ingestion of a diet containing LDPE-MPs for 90 days induced a progressive increase in oxidative stress and inflammation biomarkers in liver and plasma of S. aurata but not in erythrocytes, which tended to regain control values when not exposed to MPs for 30 days. The present study contributes to a better understanding of the toxic effects of MPs in S. aurata and highlights the usefulness of plasma that can be obtained in a minimally invasive way to monitor these effects.

Assessment of marine litter through remote sensing: recent approaches and future goals.

This bibliographic review provides an overview of techniques used to detect marine litter using remote sensing. The review classified studies in terms of platform (satellite, aircrafts, drones), sensors (passive or active), spectral (visible, infrared, microwaves), spatial resolution (<1 to >30 m), type and size (macroplastics, microplastics), or classification methodology (sighting, photointerpretation, supervised). Most studies applied satellite information to address marine litter using multi- and hyper- spectral optical sensors. The correspondence analysis on analyzed variables exhibited that aircrafts with high spatial resolution (<3 m) with optical sensors (λ = 400 to 2500 nm) seem to be the most optimum combination to target marine litter, while satellites carrying Synthetic Aperture Radar (SAR) sensors (λ = 3.1 to 5.6 cm) may detect sea-slicks associated to surfactants that might contain high concentration of microplastics. Gaps indicate that future goals in marine litter detection should be addressed with platforms including optical and SAR sensors.

Microplastic ingestion in reared aquaculture fish: Biological responses to low-density polyethylene controlled diets in Sparus aurata.

During the last years, ingestion of microplastics (MPs) has been quantified in marine species both with an ecological and commercial interest at sea and under experimental conditions, highlighting the importance to assess MP ingestion in commercially and aquaculture important species such as gilthead seabream (Sparus aurata) fish. In order to study the ingestion of MPs in a commercially valuable species, gilthead seabreams were exposed to an enriched diet with virgin and weathered low-density polyethylene (LDPE) pellets for three months followed by a detoxification period of one month of no exposure to MP enriched diets. Our results indicate that MP ingestion in these fishes increased with exposure time, and differences were found between treatments, showing the highest ingestion values after three months of exposure to MP enriched diets and in the weathered treatment. However, after one month of detoxification, no MPs were found in the gastrointestinal tracts of fish, reflecting no long-term retention of MPs in Sparus aurata digestive system. According to results from this study, exposure of fish to MP enriched diets does not affect fish size neither the Fulton's condition index as both parameters increased with time in all treatments (control, virgin and weathered). Both carbon and nitrogen isotopic signatures decreased with fish size in all treatments which could be related to an increase of nitrogen deposition efficiency in fish muscle with a high protein assimilation during the first months of Sparus aurata.

Micro- and macro-plastics in beach sediment of the Algerian western coast: First data on distribution, characterization, and source.

The accumulation of plastic debris in the Algerian coasts is due to inadequate solid waste management and the inhabitants' behavior. To quantify and characterize the plastic pollution, we collected plastic items (≥1 mm) in the sediment of nine beaches covering 124 km of the Algerian western coast. The plastic concentration varied between 7.6 ± 18.8 and 66 ± 107.28 items/m2. With 83.27%, fragments were the predominant items as micro- and macro-plastics, whereas pellets were mainly present as microplastics (14.93%); films represented 1.03%. We recorded the highest values for the number of plastic items/m2 in beaches located close to coastal villages. Regarding the number and the weight of the plastic debris, we registered significant differences between the locations. Although the plastic pollution is currently moderate in the study area, local authorities are compelled to be aware of its increase. Therefore, the improvement of the solid waste management is urgently needed.

Experimental evidence of physiological and behavioral effects of microplastic ingestion in Sparus aurata.

Increasing global research has identified microplastics (MPs) to be impacting marine organisms. The present work aimed at investigating the physiological and behavioral effects of thirty-six juvenile Sparus aurata exposed to control, virgin and weathered MPs enriched diets during a 21-day period under controlled conditions. Physiological effects were assessed in liver and brain using the following biomarkers: activities of the antioxidant enzymes catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GPx) and glutathione reductase (GRd), the detoxifying enzyme glutathione S-transferase (GST) and malondialdehyde (MDA) as indicative of lipid peroxidation. Individuals were recorded for behavior analysis (i.e. social interactions and feeding behavior). Results revealed an increase in cellular stress from control to weathered fish groups, with the virgin group showing intermediate levels in all quantified biomarkers. Significant differences were found in the liver for all biomarkers except for MDA, suggesting that exposure time to MPs in this experiment is long enough to trigger the activation of antioxidant enzymes but not to produce cell damage by lipid peroxidation. In brain tissue samples, fish from the weathered group presented significantly higher values for CAT and SOD, highlighting its function as primary antioxidants. Regarding behavioral effects, results showed that the two MPs enriched groups were significantly bolder during social interactions and, although no significantly, tended to be more active during feeding. In conclusion, MPs which have been weathered in marine environmental conditions produces a higher physiological response than virgin MPs but also, a physiological response is variable depending on the tissue analyzed. In addition, a short period to MP exposure seems to affect overall social and feeding behavior but, further research is needed to assess long-term effects of MP ingestion and its potential consequences on fish populations.

Interlaboratory comparison of microplastic extraction methods from marine biota tissues: A harmonization exercise of the Plastic Busters MPAs project.

In the framework of the Plastic Busters MPAs project, a harmonization exercise on two methods of microplastic extraction from biological samples i.e. 15% H2O2 digestion and 10% KOH digestion was carried out. The two methods were tested in four laboratories on fish gastrointestinal tracts and mussel tissues spiked with polyethylene, polypropylene and polyethylene terephthalate. The recovery percentage of microplastics for each method, species and polymer tested were overall similar among laboratories, and interlaboratory coefficient of variation was less than 11% for the majority of samples. Microplastic recovery rates for the two methods were similar for each sample tested, but overall mean interlaboratory recovery rate using KOH (96.67%) was higher than H2O2 (88.75%). Results validate the use of both methods for extracting microplastics from biota tissues. However, when comparing the two methods in terms of microplastic recovery rate, time consumed, technical difficulties and cost, digestion with 10% KOH is considered optimal.